Twist drill for drilling having a replaceable drill tip, and a replaceable drill tip for use in a twist drill

ABSTRACT

A twist drill, having a replaceable drill tip, comprising a drill bit shaft ( 1 ), a cutting insert ( 2 ) which is detachably fixed thereto and which forms the tip area of the twist drill, and comprises a flute ( 3 ) that continues into the cutting insert ( 2 ). The cutting insert rests, with a bearing surface ( 6 ) extending orthogonal to the center longitudinal axis ( 8 ) of the drill bit, on the face ( 7 ) of the drill bit shaft ( 1 ) and extends with a fixing stud ( 9 ), which centrally protrudes from the bearing surface ( 6 ), into a receiving recess ( 10 ) which is configured complementary thereto and which is provided in the face ( 7 ) of the drill bit shaft ( 1 ). At least one peripheral section ( 13 ) of the fixing stud ( 9 ) comprises a first longitudinal section ( 15 ) that, with a screw surface ( 16 ) which points away from the drill bit shaft ( 1 ), which slopes upward to the drill bit tip ( 5 ) in a direction of rotation of the drill bit, and which interacts with an opposite surface ( 19 ) on the inner wall ( 14 ) of the receiving recess ( 10 ), merges into a second longitudinal section ( 17 ).

CONTINUING APPLICATION DATA

[0001] This application is a continuation-in-part of InternationalApplication No. PCT/EP00/04851, filed on May 27, 2000, which claimspriority from Federal Republic of Germany Application No. 199 36 579.2,filed on Aug. 3, 1999. International Application No. PCT/EP00/04851 waspending as of the filing date of this application. The United States wasan elected state in International Application No. PCT/EP00/04851.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a twist drill for drilling having areplaceable drill tip. This invention further relates to a replaceabledrill tip for use in a twist drill

[0004] Additionally, this invention relates to a drill bit with areplaceable drill bit.

[0005] 2. Background Information

[0006] The modern metalworking trade primarily uses twist drills to makeborings. Depending on the application, these twist drills can differ interms of their cutting material and geometry. The cutting materialtraditionally used is increasingly being replaced by different types ofcutting material that have a significantly higher resistance toabrasion. For large drilling tools, however, a drill made entirely ofsuch abrasion-resistant materials is generally too expensive, and is noteconomical in spite of its excellent cutting performance. Alternativesare twist drills in which a drill tip made of abrasion-resistantmaterials is permanently attached to a carrier tool which is generallymade of cheaper, more traditional materials. The disadvantage of thesetools, however, is that they can be repainted only to a restrictedextent. As soon as the short cutting portion made of abrasion-resistantmaterials has been used up, the entire tool has to be scrapped.

[0007] To reduce overall costs and reduce or eliminate waste ofmaterial, it is advantageous to construct a drill with a replaceablecutting tip, as discussed herein. Replaceable cutting tips permit a userto replace the cutting tip when the cutting tip is worn down withouthaving to replace the entire drill.

[0008] On a drill bit of this type, a cutting head is detachably fixedto a drill shaft. German Patent No. 196 05 157 A1 describes a drillingtool of the prior art in which the cutting head projects by means of astud into a receiving recess on the face of the drill shaft, where it isfixed in position with a screw that is oriented at a right angle to thelongitudinal axis of the drill. On a drilling tool of the prior artdescribed in WO 98/53943, the drilling head is fixed in position in thedrill shaft with a force fit that acts in the axial direction and in thedirection of rotation of the drill.

OBJECT OF THE INVENTION

[0009] One object of the invention is to develop a twist drill fordrilling having a replaceable drill tip, as well as a replaceable drilltip for use in a twist drill.

[0010] Another object of the invention is to propose a drill bit with analternative fixing of the cutting head.

SUMMARY OF THE INVENTION

[0011] This object can be accomplished in a drill bit with a drill bitshaft and a cutting insert that forms the tip area of the drill bit andis detachably fixed to the drill bit shaft. There is at least one chipflute that is located in the drill bit shaft and extends into thecutting insert. The cutting insert is in contact with a bearing surfaceon the face of the drill shaft and extends with a fixing stud thatprojects centrally from the bearing surface into a receiving recess,which is configured complementary thereto in the face of the drillshaft. At least one peripheral segment of the fixing stud has a firstlongitudinal segment which merges with a screw surface into a secondlongitudinal section. The screw surface points away from the drillshaft, slopes upward in the direction of rotation of the drill bittoward the drill bit tip, and interacts with an opposite surface on theinner wall of the receiving recess.

[0012] The cutting head is in contact with a bearing surface against theface of the drill shaft, and extends by means a fixing stud thatprojects centrally out of the bearing surface into a complementaryreceiving recess in the face of the drill shaft. The peripheral area ofthe fixing stud that interacts with the inner wall of the recess has twolongitudinal segments, namely a first longitudinal segment which, with ascrew surface that points toward the drill tip, slopes upward in thedirection of rotation of the drill and interacts with an oppositesurface on the inner wall of the receiving recess and merges into asecond longitudinal segment. When the drill head is designed in thismanner, it can be easily inserted with its fixing stud into thereceiving recess and fixed in position opposite to the direction ofrotation of the drill. The screw surface is thereby pushed onto theopposite surface of the receiving recess and the cutting head is pressedwith its bearing surface onto the face of the drill shaft. This fixingis further strengthened when the drill is in operation.

[0013] In one preferred embodiment, the second longitudinal segment ofthe fixing stud tapers toward its free end. The receiving recess becomesnarrower by the same extent toward its base. The shaft walls that areadjacent to the receiving recess can be correspondingly thicker and morestable in this area. The tool shaft is therefore more stable with regardto a force that is exerted on the cutting head at a right angle to thelongitudinal axis of the drill than would be the case with a receivingrecess that becomes wider toward its base in an approximatelyswallowtail shape. A particularly stable mounting and centering of thefixing stud in the receiving recess is essentially guaranteed if thefree end of the fixing stud is provided with a cylindrical peripheralsurface and the area adjacent to it and extending to the screw surfaceis provided with a conical peripheral surface.

[0014] To limit the axial strain between the cutting insert and the toolshaft and to create a defined limit position for the cutting insert, inan additional embodiment of the invention, a rotation stop projects fromthe face of the drill shaft and extends into a complementary recess inthe bearing surface of the cutting insert. The bearing surfaces of thedrill shaft and the face of the tool shaft also preferably each extendat a right angle to the longitudinal axis of the drill. The screwsurface can form an angle of 90° with the longitudinal axis of thedrill. The screw surface is preferably oriented at an angle, however,and forms an angle which is <90° and >45°. The angle is preferably 60°.As a result of the inclined position of the screw surface, the cuttinginsert is pushed, in addition to the axial strain, with a force thatcenters it and is directed toward the center longitudinal axis of thedrill.

[0015] In at least one possible embodiment of the present invention, thesurfaces of the fixing stud, as well as the surfaces of the drill bitshaft that engage with the surfaces of the fixing stud, can preferablybe suitably designed to withstand torque and axial forces. Duringdrilling of an object, torque forces are exerted on a drill. Inaddition, axial forces may push and pull on the drill in the directionalong the longitudinal axis of the drill, especially during retractionof the drill from an object being drilled. The peripheral segments ofthe fixing stud may therefore preferably be designed to withstand suchforces since the peripheral segments may essentially perform a retainingfunction preferably to prevent the cutting insert from being pulled fromthe drill shaft during drilling. Conversely, in at least one possibleembodiment of the present invention, the inner surfaces of the drillshaft may also be designed preferably to withstand the forces that areacting on the cutting insert to also substantially prevent the cuttinginsert from being pulled from the drill shaft. Further, since thecutting insert may essentially be screwed into place in the drill shaftin a direction opposite the direction of rotation of the drill, torqueforces may be exerted on the cutting insert. According to at least onepossible embodiment of the present invention, the inner surfaces of thedrill shaft against which the sides of the cutting insert restpreferably must be suitably designed to essentially prevent the cuttinginsert from being further screwed into the shaft, which would mostlikely result in damage of the shaft and the insert. By strengtheningthe contact surfaces of the shaft and the cutting insert, the torque andaxial forces can be substantially withstood to prevent damage to thedrill.

[0016] In at least one other possible embodiment of the presentinvention, the chip flutes of the drill bit may each be divided intoessentially two portions: the portion of the chip flute on the drillshaft and the portion of the chip flute on the cutting insert. When thecutting insert is screwed into the drill shaft, the two chip fluteportions can be aligned to form a single chip flute surface. Although itmay preferably be desirable to design the cutting insert and the drillshaft such that the chip flute portions are exactly aligned to form achip flute that is substantially smooth and continuous, such a designmay require high precision when manufacturing the cutting inserts andthe drill shafts. It is well known, however, that any manufacturingprocess, no matter how precise, is subject to errors, tolerances andimperfections. It is therefore possible that the cutting inserts may notbe precisely manufactured due to the inherent imperfections that occurduring any manufacturing process. To account for such imperfections thatmay occur, in one possible embodiment of the present invention it maynot be necessary to have precisely aligned chip flute portions. Sincethe chip flute portions may simply serve to remove chips, exactprecision in their design may not be a requirement for proper operationof the drill. Further, the centering of the drill tip is often moreimportant to a drilling process than the precise design of the chipflutes, since an off-center drill tip will often produce a wobblingmotion of the drill during drilling, which is in many cases undesirable.The central fixing stud of the cutting insert can provide a centeringfunction that essentially centers the drill tip along the centrallongitudinal axis of the drill bit. The present invention, in at leastone possible embodiment, therefore teaches that as long as the drill tipof the cutting insert is designed to lie on the central longitudinalaxis, it may be possible for the chip flute portions to be slightlymisaligned without substantially affecting the performance of the drill.

[0017] Drills such as the type described above may be used, in at leastone possible embodiment, to cut various materials, such as metals, wood,plastics, composites, polymers, steel, and other hard materials. Inaddition, such drills may also possibly be used in machine-operated,automatic drilling systems, such as numerically-controlled drillingsystems on assembly lines. By having replaceable cutting or drillinginserts, it may be possible in at least one possible embodiment of thepresent invention, to substantially maintain the overall length of thedrill by replacing the cutting inserts when they become worn. Bysubstantially maintaining the length of the drill, it may not benecessary to reconfigure or reprogram the machinery using the drill inthe automatic drilling process since the drill will not substantiallychange in length.

[0018] The above-discussed embodiments of the present invention will bedescribed further hereinbelow. When the word “invention” is used in thisspecification, the word “invention” includes “inventions”, that is theplural of “invention”. By stating “invention”, the Applicant does not inany way admit that the present application does not include more thanone patentably and non-obviously distinct invention, and maintains thatthis application may include more than one patentably and non-obviouslydistinct invention. The Applicant hereby asserts that the disclosure ofthis application may include more than one invention, and, in the eventthat there is more than one invention, that these inventions may bepatentable and non-obvious one with respect to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention is explained in greater detail below with referenceto the exemplary embodiments illustrated in the accompanying drawings,in which:

[0020]FIG. 1 shows the upper segment of a drill bit with three chipflutes and a corresponding three-edged cutting insert, in a side view;

[0021]FIG. 2 is a side view of the cutting insert illustrated in FIG. 1;

[0022]FIG. 3 is a plan view from overhead of the cutting insert in thedirection of the arrow III in FIG. 2;

[0023]FIG. 4 is a side view of a drill shaft as illustrated in FIG. 1,with the cutting insert removed;

[0024]FIG. 5 is a plan view from overhead of the face of the tool shaftin the direction of the arrow 5 in FIG. 4;

[0025]FIG. 6 shows an additional embodiment of a cutting insert inlongitudinal section;

[0026]FIG. 7 shows an additional embodiment of a cutting insert inlongitudinal section;

[0027]FIG. 8 is a side view of the upper portion of a drill bit with atwo-edged cutting insert;

[0028]FIG. 9 is a side view of the upper longitudinal segment of thedrill with the cutting insert removed;

[0029]FIG. 10 is a plan view from overhead in the direction of the arrowX in FIG. 9;

[0030]FIG. 11 shows a two-edged cutting insert in a side view;

[0031]FIG. 12 is a plan view from overhead in the direction indicated bythe arrow XII in FIG. 11; and

[0032]FIG. 13 is a view of the drill in FIG. 8 with additional featuresaccording to at least one possible embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] The drill bits illustrated in the accompanying drawings arecomposed of a drill shaft 1 and a cutting insert 2. The cutting insert 2a on the drill illustrated in FIGS. 1 to 5 is three-edged. Accordingly,there are a total of three chip flutes 3 in the drill shaft 1, whichcontinue with chip flute segments 3 a into the cutting insert 2 a. Thecutting insert has three major cutting edges 4 which—as can be seen inparticular in the plan view from overhead in FIG. 3—are oriented inapproximately a star shape and converge in the drill tip 5. The threeedges of the cutting insert mean that the cutting insert, likewise shownin the plan view from overhead in FIG. 3, has approximately the shape ofa trifurcated star.

[0034] The cutting insert 2 a has a flat bearing surface 6, which is inflat contact against the face 7 of the drill shaft 1. The bearingsurface 6 and the face 7 extend at a right angle with respect to thecenter longitudinal axis 8 of the drill bit. Shaped onto the bearingsurface 6 is a central fixing stud 9, which extends in the direction ofthe center longitudinal axis 8. When the drill bit is inserted, thefixing stud 9 lies in a complementary configured receiving recess 10 inthe drill shaft 1, where it is effectively fixed by axial undercuts. Thereceiving recess 10 emerges into the chip flutes 3 with lateral openings11 that extend to the face 7. When the drill bit is inserted asillustrated in FIG. 1, the cutting surface areas that form the chipflute segments 3 a and the chip flute 3 of the drill shaft 1 are alignedwith one another, whereby they are interrupted only by the joint 12between the cutting insert 2 a and the drill shaft 1.

[0035] The chip flute segments 3 a divide the fixing stud 9 into threeperipheral segments 13, which interact with the inside walls 14 of thereceiving recess 10. The fixing stud 9 has a first longitudinal segment15 which merges with a screw surface 16 into a second longitudinalsegment 17. The screw surface 16 points toward the drill tip 5 andprojects in the manner of a radial shoulder from the peripheral segment13. The screw surface 16 slopes upward in the direction of rotation 18of the drill bit toward the drill tip 5 and interacts with acomplementary configured opposite surface 19 on the inside walls 14 ofthe receiving recess 10. To essentially fix the cutting insert to thedrill shaft 1, the cutting insert is inserted with the fixing stud 9into the receiving recess 10 so that its peripheral segments 13 arelocated in the vicinity of the openings 11. As the result of a rotationin the direction opposite to the direction of rotation 18 of the drillbit, the screw surfaces 16 arrive below the opposite surfaces 19 on theinner walls 14, as a result of which the cutting insert is pressed inthe direction indicated by the arrow 20 with its bearing surface 6against the face 7.

[0036] The surface of the second longitudinal segment 17 that interactswith the inner walls 14 can be a partly cylindrical surface asillustrated in FIG. 6. In the exemplary embodiment illustrated in FIG.7, the second longitudinal segment 17 tapers conically toward the drillshaft. However, special preference is given to the configurationillustrated in FIG. 2, in which adjacent to the screw surface 16 thereis a conical segment 21, which merges into a cylindrical segment 22. Thecylindrical segment 22 effects a centering of the cutting insert 2 a inthe receiving recess 10. The diameter of the cylindrical segment 22 canbe relatively small compared to the segments adjacent to it toward thetip and that have the screw surfaces 16 necessary for the axial bracing.Accordingly, the area 23 of the receiving recess 10 that interacts withthe cylindrical segment 22 can also have a small inside diameter. Thatin turn means a greater wall thickness 24 in the area 23 and thusincreased stability. Especially in the area 23 have a greater effect onaccount of the lever effect. However, the greater wall thickness 24 inthis area guarantees increased stability of the drill shaft 1.

[0037] To further explain, the torque forces act on the cutting insert 2a during a drilling procedure. Due to the lever effect, a large portionof the torque forces are exerted at the transition between the bearingsurface 6 and the first longitudinal segment 15. Therefore, it isadvantageous for the fixing stud 9 to have an increased thickness atthat particular area. Further, since the majority of the torque forcesare concentrated on that particular area, it is possible for the fixingstud 9 to decrease in thickness in the area of the cylindrical segment22. In addition, by decreasing the thickness of the fixing stud 9, it isthereby possible to have an increased thickness of the shaft 1 in thearea 23. As torque forces are exerted on the cutting insert 2 a, forceis also exerted on the portions of the shaft 1 about the recess 10. Alsodue to the lever effect, the majority of the force is exerted on thearea 23 near the bottom of the recess 10. By decreasing the thickness ofthe fixing stud 9 at the area 23, the wall thickness 24 can beconsequently increased to compensate for the greater torque forcesexerted in that particular area 23. The lever effect therefore can beaccounted for by increasing thickness of the shaft 1 and the fixing stud9 at the areas where the concentration of force is the greatest.

[0038] The screw surfaces 16 on the fixing stud 9 of a cutting insert 2can basically form an angle of 90° with the center longitudinal axis 8of the drill or of the cutting insert. However, preference is given toscrew surfaces 16 that are oriented at an angle and form an angle α withthe center longitudinal axis 8 which is <90° and ≧45°.

[0039] FIGS. 8 to 12 show a drill bit with two chip flutes andaccordingly a two-edged cutting insert 2 b. The configuration of thefixing stud 9 and of the receiving recess 10 of this drill bit is thesame as that of the drill bit described above. One difference is thattwo rotation stops 25 project from the face 7 a of the drill shaft 1.The rotation stops 25 are diametrically opposite each other and arerealized with four surfaces in an essentially wedge shape. Their outsidesurface 26 is formed by the peripheral surface of the drill shaft 1.Their inside surface 27 interacts with a complementary configuredopposite surface 28, which is part of the wall of a recess 29 in thebearing surface 6 of the cutting insert 2 b, which recess 29 holds therotation stop 25. The rotation stops also have two inclined surfaces,whereby the one inclined surface 30 points in the direction of rotation18 of the drill bit and merge into a face 7 a. The other inclinedsurface 31 points opposite to the direction of rotation 18 of the drillbit and is a partial surface of the face 32 that forms the chip flute 3.The inclined surface 30 interacts with an inclined surface 33 that isformed from the wall of the recess 29 and acts as an opposite bearingsurface.

[0040]FIG. 13 is a view of the drill shown in FIG. 8 with additionalfeatures according to at least one possible embodiment of the presentinvention. The drill bit has a drill shank portion 101 that is insertedinto a tool chuck 102. The tool chuck 102 holds the drill bit andprovides a driving force to rotate the drill during a drilling process.The drill shown has a two-edged cutting insert design, but is not theonly possible embodiment. This drill bit and chuck configuration mayalso be used with cutting inserts and bits with more than two edges,such as a cutting insert with three edges, as shown in FIGS. 1-3.

[0041] One feature (or aspect) of an embodiment of the invention residesbroadly in a drill bit with a drill bit shaft (1) and a cutting insertthat forms the tip area of the drill bit and is detachable fixed to thedrill bit shaft, and at least one chip flute (3) that is located in thedrill bit shaft (1) and extends into the cutting insert (2), whereby thecutting insert is in contact with a bearing surface (6) on the face (7)of the frill shaft (1) and extends with a fixing stud (9) that projectscentrally from the bearing surface (6) into a receiving recess (10)which is configured complementary thereto in the face (7) of the drillshaft (1), characterized by the fact that at least one peripheralsegment (13) of the fixing stud (9) has a first longitudinal segment(15) which with a screw surface (16) that points away from the drillshaft (1), slopes upward in the direction of rotation (18) of the drillbit toward the drill bit tip (5) and interacts with an opposite surface(19) on the inner wall (14) of the receiving recess (10), merges into asecond longitudinal section (17).

[0042] Another feature (or aspect) of an embodiment of the inventionresides broadly in a drill bit, characterized by the fact that thesecond longitudinal segment (17) tapers toward its free end.

[0043] Yet another feature (or aspect) of an embodiment of the inventionresides broadly in a drill bit, characterized by a first stud segment(22) forming the free end with a cylindrical peripheral surface, and asecond segment (21) that has a conical peripheral surface and extends tothe screw surface (16).

[0044] Still another feature (or aspect) of an embodiment of theinvention resides broadly in a drill bit characterized by a rotationstop (25) that projects from the face (7) of the drill shaft (1) andprojects into an essentially complementary shaped recess in the bearingsurface (6) of the cutting insert (2).

[0045] A further feature (or aspect) of an embodiment of the inventionresides broadly in a drill bit, characterized by the fact that the screwsurface (16) forms an angle (α) of 90° to 45° with the longitudinal axis(8) of the drill bit.

[0046] Another feature (or aspect) of an embodiment of the inventionresides broadly in a drill bit, characterized by an angle (α) of 60°.

[0047] The components disclosed in the various publications, disclosedor incorporated by reference herein, may be used in the embodiments ofthe present invention, as well as equivalents thereof.

[0048] The appended drawings in their entirety, including alldimensions, proportions and/or shapes in at least one embodiment of theinvention, are accurate and are hereby included by reference into thisspecification.

[0049] All, or substantially all, of the components and methods of thevarious embodiments may be used with at least one embodiment or all ofthe embodiments, if more than one embodiment is described herein.

[0050] All of the patents, patent applications and publications recitedherein, and in the Declaration attached hereto, are hereby incorporatedby reference as if set forth in their entirety herein.

[0051] The corresponding foreign and international patent publicationapplications, namely, Federal Republic of Germany Application No. 199 36579.2, filed on Aug. 3, 1999, having inventor Ulrich KRENZER, and DE-OS199 36 579.2, having inventor Ulrich KRENZER, and DE-PS 199 36 579.2,having inventor Ulrich KRENZER, and International Application No.PCT/EP00/04851, filed on May 27, 2000, having inventor Ulrich KRENZER,as well as their published equivalents, and other equivalents orcorresponding applications, if any, in corresponding cases in theFederal Republic of Germany and elsewhere, and the references anddocuments cited in any of the documents cited herein, such as thepatents, patent applications and publications, are hereby incorporatedby reference as if set forth in their entirety herein.

[0052] All of the references and documents, cited in any of thedocuments cited herein, are hereby incorporated by reference as if setforth in their entirety herein. All of the documents cited herein,referred to in the immediately preceding sentence, include all of thepatents, patent applications and publications cited anywhere in thepresent application.

[0053] The details in the patents, patent applications and publicationsmay be considered to be incorporable, at applicant's option, into theclaims during prosecution as further limitations in the claims topatentably distinguish any amended claims from any applied prior art.

[0054] The following U.S. Patents regarding drills and/or drill insertsare hereby incorporated by reference as if set forth in their entiretyherein: U.S. Pat. No. 5,800,100, having attorney docket no.NHL-KEH-03-NP, issued to Krenzer on Sep. 1, 1998; NHL-KEH-06, issued toKammermeier on Nov. 3, 1998; U.S. Pat. No. 5,967,710, having attorneydocket no. NHL-KEH-02-NP, issued to Krenzer on Oct. 9, 1999; U.S. Pat.No. 6,045,301, having attorney docket no. NHL-KEH-04 US, issued toKammermeier et al. on Apr. 4, 2000; U.S. Pat. No. 6,116,825, havingattorney docket no. NHL-KEH-05 US, issued to Kammermeier et al. on Sep.12, 2000; U.S. Pat. No. 6,164,879, having attorney docket no.NHL-KEH-02-NP-D, issued to Krenzer on Dec. 26, 2000; U.S. Pat. No.6,210,083, having attorney docket no. NHL-KEH-05-C US, issued toKammermeier et al. on Apr. 3, 2001; U.S. Pat. No. 6,231,276, havingattorney docket no. NHL-KEH-09 US, issued to Muller et al. on May 15,2001; U.S. Pat. No. 5,904,455, having attorney docket no. NHL-KEH-08,issued to inventors Krenzer et al. on May 18, 1999; and U.S. Pat. No.6,309,149, having attorney docket no. NHL-KEH-12 US, issued to inventorBORSCHERT on Oct. 30, 2001.

[0055] The following U.S. Patent Applications regarding drills and/ordrill inserts are hereby incorporated by reference as if set forth intheir entirety herein: Ser. No. 09/521,134, having attorney docket no.NHL-KEH-13 US, having inventors Gebhard MÜLLER and Horst JAGER, filed onMar. 8, 2000; Ser. No. 09/927,921, having attorney docket no. NHL-KEH-14US, having inventors Bernhard Walter BORSCHERT, Jochen STIES, DieterHermann MUHLFRIEDEL, and Karl-Heinz WENDT, filed on Aug. 10, 2001; Ser.No. 09/935,078, having attorney docket no. NHL-KEH-15, having inventorsHans-Wilm HEINRICH, Manfred WOLF, and Dieter SCHMIDT, filed on Aug. 22,2001; Ser. No. 09/966,735, having attorney docket no. NHL-KEH-16 US,having inventor Ulrich KRENZER, filed on Sep. 28, 2001; and Ser. No.10/008,528, having attorney docket no. NHL-KEH-17, having inventor RudiHARTLOHNER, filed on Nov. 5, 2001;.

[0056] Some examples of twist drills that may possibly be utilized oradapted for use in at least one possible embodiment of the presentinvention may possibly be found in the following U.S. patents: U.S. Pat.No. 4,209,275, issued to Kim on Jun. 24, 1980; U.S. Pat. No. 4,556,347,issued to Barish on Dec. 3, 1985; U.S. Pat. No. 4,688,972, issued toKubota on Aug. 25, 1987; U.S. Pat. No. 4,756,650, issued to Wakihira etal. on Jul. 12, 1988; U.S. Pat. No. 4,762,445, issued to Bunting et al.on Aug. 9, 1988; U.S. Pat. No. 5,230,593, issued to Imanaga et al. onJul. 27, 1993; U.S. Pat. No. 5,350,261, issued to Takaya et al. on Sep.27, 1994; U.S. Pat. No. 5,442,979, issued to Hsu on Aug. 22, 1995; U.S.Pat. No. 5,678,960, issued to Just et al. on Oct. 21, 1997; U.S. Pat.No. 5,931,615, issued to Wiker on Aug. 3, 1999; and U.S. Pat. No.6,283,682, issued to Plummer on Sep. 4, 2001.

[0057] Some examples of other drills and drill inserts, features ofwhich may possibly be utilized or adapted for use in at least onepossible embodiment of the present invention may possibly be found inthe following U.S. patents: U.S. Pat. No. 4,072,438, issued to Powers onFeb. 7, 1978; U.S. Pat. No. 4,131,383, issued to Powers on Dec. 26,1978; U.S. Pat. No. 4,220,429, issued to Powers et al. on Sep. 2, 1980;U.S. Pat. No. 4,563,113, issued to Ebenhoch on Jan. 7, 1986; U.S. Pat.No. 5,173,014, issued to Agapiou et al. on Dec. 22, 1992; U.S. Pat. No.5,236,291, issued to Agapiou et al. on Aug. 17, 1993; U.S. Pat. No.5,807,041, issued to Lindblom on Sep. 15, 1998; U.S. Pat. No. 5,947,659,issued to Mays on Sep. 7, 1999; and U.S. Pat. No. 6,071,046, issued toHecht et al. on Jun. 6, 2000.

[0058] Some examples of drills and/or drill bits with tungsten carbidethat may possibly be utilized or adapted for use in at least onepossible embodiment of the present invention may possibly be found inthe following U.S. patents: U.S. Pat. No. 6,135,218, issued to Deane etal. on Oct. 24, 2000; U.S. Pat. No. 6,029,544, issued to Katayama onFeb. 29, 2000; U.S. Pat. No. 5,979,571, issued to Scott et al. on Nov.9, 1999; U.S. Pat. No. 5,836,409, issued to Vail, III on Nov. 17, 1998;U.S. Pat. No. 4,241,483, issued to Voitas on Dec. 30, 1980; U.S. Pat.No. 4,200,159, issued to Peschel et al. on Apr. 29, 1980; and U.S. Pat.No. 4,169,637, issued to Voitas on Oct. 2, 1979.

[0059] Some examples of drills and/or drill bits with titanium carbidethat may possibly be utilized or adapted for use in at least onepossible embodiment of the present invention may possibly be found inthe following U.S. patents: U.S. Pat. No. 5,882,152, issued to Janitzkion Mar. 16, 1999 and U.S. Pat. No. 4,211,294, issued to Multakh on Jul.8, 1980.

[0060] Some examples of high strength steel that may possibly beutilized or adapted for use in at least one possible embodiment of thepresent invention may possibly be found in the following U.S. patents:U.S. Pat. No. 4,578,113, issued to Rana et al. on Mar. 25, 1986; U.S.Pat. No. 4,720,307, issued to Matsumoto et al. on Jan. 19, 1988; U.S.Pat. No. 4,814,141, issued to Imai et al. on Mar. 21, 1989; U.S. Pat.No. 4,826,543, issued to Yano et al. on May 2, 1989; U.S. Pat. No.4,956,025, issued to Koyama et al. on Sep. 11, 1990; U.S. Pat. No.5,651,938, issued to Thomson et al. on Jul. 29, 1997; U.S. Pat. No.5,772,957, issued to Thomson et al. on Jun. 30, 1998; and U.S. Pat. No.5,798,004, issued to Tamehiro et al. on Aug. 25, 1998.

[0061] Some examples of numerical control systems involving drills ordrilling processes may possibly be found in the following U.S. Patents:U.S. Pat. No. 6,232,736, entitled “Numerical control machine toolpositioning system”; U.S. Pat. No. 6,107,768, entitled “Numericalcontrol apparatus for a machine tool”; U.S. Pat. No. 6,036,347, entitled“Numerical control information generator for controlling machine toolprocesses which require tool exchanges”; U.S. Pat. No. 5,815,400,entitled “Machining method using numerical control apparatus”; U.S. Pat.No. 5,532,932, entitled “Numerical control unit”; U.S. Pat. No.5,493,502, entitled “Numerical control unit for controlling a machinetool to machine a workpiece at an instructed feed rate along linear androtational axes”; U.S. Pat. No. 4,972,322, entitled “Method forpreparing numerical control data for a machine tool”; U.S. Pat. No.4,914,364, entitled “Numerical control apparatus”; U.S. Pat. No.4,862,380, entitled “Numerical control unit”; U.S. Pat. No. 4,831,906,entitled “Numerical control machine”; U.S. Pat. No. 4,794,311, entitled“Numerical control system”; U.S. Pat. No. 4,788,481, entitled “Numericalcontrol apparatus”; U.S. Pat. No. 4,751,652, entitled “Numerical controldrilling restart control system”; U.S. Pat. No. 4,719,579, entitled“Numerical control method”; U.S. Pat. No. 4,667,294, entitled “Numericalcontrol apparatus”; U.S. Pat. No. 4,624,607, entitled “Computednumerical control drilling machine”; U.S. Pat. No. 4,588,339, entitled“Tool holder for a cutting machine provided with numerical control”;U.S. Pat. No. 4,549,270, entitled “Method of controlling selection oftools in a quadriaxial numerical control lathe”; U.S. Pat. No.4,547,854, entitled “Method of controlling lineup of tools in numericalcontrol machine tool”; U.S. Pat. No. 4,199,814, entitled “Computernumerical control machine tool”; and U.S. Pat. No. 4,149,235, entitled“Computer numerical control system for machine tool.

[0062] The invention as described hereinabove in the context of thepreferred embodiments is not to be taken as limited to all of theprovided details thereof, since modifications and variations thereof maybe made without departing from the spirit and scope of the invention.NOMENCLATURE  1 Drill shaft  2 Cutting insert  3 Chip flute  3a Chipflute segment  4 Major cutting edge  5 Drill tip  6 Bearing surface  7Face  8 Center longitudinal axis  9 Fixing stud 10 Receiving recess 11Opening 12 Joint 13 Peripheral segment 14 Inside wall 15 Firstlongitudinal segment 16 Screw surface 17 Second longitudinal segment 18Direction of rotation of drill bit 19 Opposite surface 20 Arrow 21Conical segment 22 Cylindrical segment 23 Area 24 Wall thickness 25Rotation stop 26 Outside surface 27 Inside surface 28 Opposite surface29 Recess 30 Inclined surface 31 Inclined surface 32 Face 33 Inclinedsurface α Angle

What is claimed is:
 1. A twist drill comprising: a shaft comprising afirst end and a second end disposed opposite said first end; said firstend of said shaft comprising a shank portion being configured to beinserted into and held by a chuck; a replaceable drilling insert beingremovably attached to said second end of said shaft; said drillinginsert comprising a drill tip being configured to cut an object; atleast a first chip flute and a second chip flute; each of said first andsecond chip flutes comprising a first chip flute portion disposed onsaid shaft and a second chip flute portion disposed on said drillinginsert; said second end of said shaft comprising a recess; said recesscomprising a bottom wall and at least one side wall disposed betweensaid bottom wall and said end face; said drilling insert comprising afixing stud; said fixing stud being configured and disposed to beinserted into said recess to removably attach said drilling insert tosaid shaft; said drilling insert comprising a bearing surface disposedabout said fixing stud; said shaft comprising an end face disposed aboutsaid recess; said drilling insert bearing surface being complementary tosaid shaft end face and being configured and disposed to contact andrest against said shaft end face; said fixing stud comprising at leastone projection; said at least one projection being in the shape of aportion of a screw thread and being configured to slope away from saidshaft toward said drill tip in the manner of a screw thread; said atleast one projection being disposed to run substantially less than 180degrees around a section of the perimeter of said fixing stud from saidfirst chip flute to said second chip flute; said at least one side wallcomprising a grooved portion; the shape of said grooved portion of saidrecess being complementary to the shape of said at least one projectionof said fixing stud; said grooved portion being disposed to runsubstantially less than 180 degrees around a section of said at leastone side wall from said first chip flute to said second chip flute; saiddrilling insert being configured to be rotated, upon insertion into saidrecess, substantially less than 180 degrees to engage said groovedportion, in a screwing motion, with said at least one projection toscrew said drilling insert into said recess to tighten and sufficientlyfirmly seat said drilling insert in said recess to prepare the twistdrill for drilling; and said fixing stud comprising a first portionbeing disposed substantially transverse to said bearing surface andbetween said bearing surface and said at least one projection.
 2. Adrill comprising: a shaft; a replaceable drilling insert being removablyattached to said shaft; said drilling insert comprising a drill tipbeing configured to cut an object; at least one chip flute; said atleast one chip flute comprising a first chip flute portion disposed onsaid shaft and a second chip flute portion disposed on said drillinginsert; said shaft comprising a recess configured and disposed toreceive said drilling insert and to hold said drilling insert duringdrilling; said drilling insert comprising an extending portion beingconfigured and disposed to extend into said recess of said shaft; saidextending portion comprising at least one projection; said at least oneprojection being in the shape of a portion of a screw thread and beingdisposed to run less than 180 degrees around a section of the perimeterof said extending portion; said recess of said shaft comprising at leastone grooved portion; said grooved portion being disposed to run lessthan 180 degrees around a section of the interior of said recess andbeing configured to be engaged by said at least one projection; and saiddrilling insert and said shaft each being configured to be relativelyrotated, upon insertion of said drilling insert into said recess,substantially less than 180 degrees to engage said grooved portion, in ascrewing motion, with said at least one projection to screw togethersaid drilling insert and said shaft to tighten and sufficiently firmlyseat said drilling insert in said recess to prepare the drill fordrilling.
 3. A replaceable drill insert configured to be removablyattached to a drill shaft, said drill insert comprising: a drill tipbeing configured to cut an object; an extending portion being configuredto extend into a recess in a drill shaft to removably attach said drillinsert to a drill shaft and to hold said drill insert in a drill shaftduring drilling; said extending portion comprising at least oneprojection; said at least one projection being in the shape of a portionof a screw thread and being disposed to run less than 360 degrees arounda section of the perimeter of said extending portion; said at least oneprojection being configured to project into and engage a grooved portionin a recess in a drill shaft; and said drill insert being configured tobe relatively rotated with a drill shaft, upon insertion of said drillinsert into a recess in a drill shaft, less than 360 degrees to engage agrooved portion of a recess in a drill shaft with said at least oneprojection to screw together said drill insert and a drill shaft totighten and sufficiently firmly seat said drill insert in a drill shaftto prepare a drill for drilling.
 4. A method of using a drill with areplaceable drill insert, said drill insert comprising: a drill tipbeing configured to cut an object; an extending portion being configuredto extend into a recess in a drill shaft to removably attach said drillinsert to a drill shaft and to hold said drill insert in a drill shaftduring drilling; said extending portion comprising at least oneprojection; said at least one projection being in the shape of a portionof a screw thread and being disposed to run less than 360 degrees arounda section of the perimeter of said extending portion; said at least oneprojection being configured to project into and engage a grooved portionin a recess in a drill shaft; and said drill insert being configured tobe relatively rotated with a drill shaft, upon insertion of said drillinsert into a recess in a drill shaft, less than 360 degrees to engage agrooved portion of a recess in a drill shaft with said at least oneprojection to screw together said drill insert and a drill shaft totighten and sufficiently firmly seat said drill insert in a drill shaftto prepare a drill for drilling; said method comprising the steps of:inserting said drill insert into a recess in a drill shaft; aligningsaid at least one projection with a grooved portion in a recess in adrill shaft; relatively rotating said drill insert and a drill shaftless than 180 degrees to engage a grooved portion of the drill shaftwith said at least one projection to screw together said drill insertand the drill shaft to tighten and sufficiently firmly seat said drillinsert in the drill shaft to prepare a drill for drilling; removing saiddrill insert from a drill shaft by unscrewing said drill insert uponsaid drill insert being substantially worn as a result of drilling;inserting a new drill insert into a recess in a drill shaft; aligning atleast one projection of said new drill insert with a grooved portion ina recess in a drill shaft; and relatively rotating said new drill insertand a drill shaft less than 180 degrees to engage a grooved portion ofthe drill shaft with said at least one projection of said new drillinsert to screw together said new drill insert and the drill shaft totighten and sufficiently firmly seat said new drill insert in the drillshaft to prepare a drill for drilling.
 5. Drill bit with a drill bitshaft (1) and a cutting insert that forms the tip area of the drill bitand is detachable fixed to the drill bit shaft, and at least one chipflute (3) that is located in the drill bit shaft (1) and extends intothe cutting insert (2), whereby the cutting insert is in contact with abearing surface (6) on the face (7) of the frill shaft (1) and extendswith a fixing stud (9) that projects centrally from the bearing surface(6) into a receiving recess (10) which is configured complementarythereto in the face (7) of the drill shaft (1), characterized by thefact that at least one peripheral segment (13) of the fixing stud (9)has a first longitudinal segment (15) which with a screw surface (16)that points away from the drill shaft (1), slopes upward in thedirection of rotation (18) of the drill bit toward the drill bit tip (5)and interacts with an opposite surface (19) on the inner wall (14) ofthe receiving recess (10), merges into a second longitudinal section(17).
 6. Drill bit as claimed in claim 5, characterized by the fact thatthe second longitudinal segment (17) tapers toward its free end. 7.Drill bit as claimed in claim 6, characterized by a first stud segment(22) forming the free end with a cylindrical peripheral surface, and asecond segment (21) that has a conical peripheral surface and extends tothe screw surface (16).
 8. Drill bit as claimed in claim 5,characterized by a rotation stop (25) that projects from the face (7) ofthe drill shaft (1) and projects into an essentially complementaryshaped recess in the bearing surface (6) of the cutting insert (2). 9.Drill bit as claimed in claim 6, characterized by a rotation stop (25)that projects from the face (7) of the drill shaft (1) and projects intoan essentially complementary shaped recess in the bearing surface (6) ofthe cutting insert (2).
 10. Drill bit as claimed in claim 7,characterized by a rotation stop (25) that projects from the face (7) ofthe drill shaft (1) and projects into an essentially complementaryshaped recess in the bearing surface (6) of the cutting insert (2). 11.Drill bit as claimed in claim 5, characterized by the fact that thescrew surface (16) forms an angle (α) of 90° to 45° with thelongitudinal axis (8) of the drill bit.
 12. Drill bit as claimed inclaim 6, characterized by the fact that the screw surface (16) forms anangle (α) of 90° to 45° with the longitudinal axis (8) of the drill bit.13. Drill bit as claimed in claim 7, characterized by the fact that thescrew surface (16) forms an angle (α) of 90° to 45° with thelongitudinal axis (8) of the drill bit.
 14. Drill bit as claimed inclaim 8, characterized by the fact that the screw surface (16) forms anangle (α) of 90° to 45° with the longitudinal axis (8) of the drill bit.15. Drill bit as claimed in claim 9, characterized by the fact that thescrew surface (16) forms an angle (α) of 90° to 45° with thelongitudinal axis (8) of the drill bit.
 16. Drill bit as claimed inclaim 10, characterized by the fact that the screw surface (16) forms anangle (α) of 90° to 45° with the longitudinal axis (8) of the drill bit.17. Drill bit as claimed in claim 11, characterized by an angle (α) of60°.
 18. Drill bit as claimed in claim 12, characterized by an angle (α)of 60°.
 19. Drill bit as claimed in claim 13, characterized by an angle(α) of 60°.
 20. Drill bit as claimed in claim 16, characterized by anangle (α) of 60°.